"Gee Lattice Topos" were prepared for "Operation Overlord" on a Mercator projection at a scale of 1:500,000. They are overprinted with hyperbolic curves relating to wireless transmission signals from mobile "Gee" sets. These mobile “Gee” stations were established on the Continent as soon as sites for them had been cleared by the ground forces. The charts differ from standard air maps in that basic detail is printed in broken black, layer tints were omitted, pastel tints were used for woods, water and roads, and the hyperbolic curves were overprinted in strong colours. Soon after "D-Day," transmission signals from the mobile "Gee" chains were utilized by the heavy bombers of Bomber Command and Eighth U.S.A.A.F. and by the carriers of both Ninth U.S. Troop Carrier Command and Transport Command R.A.F.